1. Field of the Invention
The present invention relates to an apparatus and a method for controlling transmission power of a mobile communication terminal capable of improving the terminal power efficiency.
2. Description of the Related Art
The mobile communication terminal moves within a service region formed by a base station (BS). The mobile communication terminal enables radio paging and access to another terminal utilizing switches controlled by a mobile switching center (MSC). A mobile communication terminal performs data communication which may include a symbol, number, character, or the like, and/or a multimedia communication which may include a video signal and a voice communication.
FIG. 1 is a block diagram illustrating an apparatus for controlling the transmission power of a mobile communication terminal in accordance with the related art.
Referring to FIG. 1, the related art apparatus comprises a central processing unit (CPU) 10 for measuring the power level of a received signal. The CPU 10 outputs a gain value based on the measured power level of the received signal. A driver amplifier 20 amplifies a transmission signal in accordance with the gain value. A power amplifier 30 amplifies an output signal from the driver amplifier 20. A power supply unit 40 using an enable signal turns on/off a power source which is applied to the power amplifier upon transmission of the amplified output signal.
FIG. 2 is a flow chart illustrating a method for controlling transmission power of a mobile communication terminal in accordance with the related art.
Referring to FIG. 2, the method includes measuring a power level of a received signal (S21), determining a gain value of a driver amplifier in accordance with the determined power level of the received signal (S23), amplifying a transmission signal in accordance with the determined gain value to produce an output transmission signal, and amplifying the outputted transmission signal using a power amplifier (S27).
In the related art, the CPU 10 measures a power level of a received signal (S21) and outputs a gain control signal. The gain control signal controls a gain value of a driver amplifier 20. The gain value depends on a measured power level of the received signal (S23). The CPU 10 provides a row access strobe random access memory (RAS RAM) 11 for storing the gain value in accordance with the measured power level of the received signal.
The driver amplifier 20 amplifies the transmission signal depending on the outputted gain control signal. The driver amplifier 20 outputs an amplified transmission signal to the power amplifier 30 (S25). The power supply unit 40 is turned-on by an enable signal and applies a specified voltage Vcc to the power amplifier 30. The enable signal is determined in accordance with whether the transmission signal has been transmitted.
The power amplifier 30 amplifies the outputted transmission signal in accordance with the specified voltage Vcc (S27). A duplex element 50 transmits the amplified outputted transmission signal, from the power amplifier 30, through an antenna 60.
The CPU 10 controls the power amplifier 30 using an outputted control signal PA_RO. The power amplifier 30 is driven to either a high gain mode or a low gain mode. The power amplifier 30 is driven in the low gain mode when the power level of the received signal is lower than a preset value. The power amplifier 30 is driven in the high gain mode when the power level of the received signal is greater than the preset value.
In summary, the voltage Vcc turns on/off power to the power amplifier 30 in accordance with whether the transmission signal is to be transmitted. To conserve electrical power and increase overall efficiency of the mobile terminal, the related art mobile terminal communicates with a low signal output level in a strong electric field area. In a weak electric field environment, the related art mobile terminal utilizes a high signal output level. Hence, there is a need for improvements in the related art apparatus and method for further increasing the efficiency of the mobile terminal and providing other advantages over the related art.